Operator&#39;s telephone circuit



FeB. I8, 1936.

E. DIETZE OPERATORS TELEPHONE CIRCUIT Filed April 21, 1934 Operator-5s ZlephbneSet Superuzlyon'; m fele ohvme Set 15 other Carol Circuits I Line 8 INVENTOR 6 ATTORNEY Patented Feb. 18, 1936 UNITED STATES usten PATENT OFFIEE OPERATORS TELEPHONE CIRCUIT Application April 21, 1934, Serial No. 721,809

Claims.

This invention relates to operators telephone circuits, and particularly to a system for monitoring on such circuits without impairing the operators transmission over such circuit during the 5 monitoring operation.

It is common practice now on the part of the supervisor or her assistant in monitoring on the operator at a telephone switchboard, for the purpose of instructing the operator or assisting her in the handling of calls, to use a special telephone set equipped with a high impedance receiver in order that a minimum bridging loss will be introduced when the supervisors telephone set is connected to the operators telephone circuit in parallel with the operators own telephone set. Ob-

viously, such high impedance receiver does not permit as good reception as the lower impedance receiver used by the switchboard operator. Consequently, when the supervisor wishes to operate at the switchboard, that is, to take her place .at the switchboard as an operator, or wishes to talk to a party with which the operators telephone circuit is connected, during her work as a supervisor, it is necessary for the supervisor to use a diiferent telephone set from that employed by her in the monitoring operation, that is, to use .a set having a receiver of lower impedance so that her reception may not be impaired.

My invention resides in an arrangement for monitoring on an operator at a switchboard position by using a telephone set which, in its essential elements, is identical with the telephone set used by the operator .at such position so that the same telephone set may be used both for monitoring as well as for operating at the switchboard. The arrangement is such that when monitoring the impedance of the receiver of the supervisors telephone set is made substantially high relative to the impedance of the operators receiver so that substantially no receiving loss is caused to the operator when a supervisor or other person listens in on the conversation.

Other objects of this invention will be apparent from the following description when read in connection with the attached drawing which shows one form of embodiment of the invention in connection with a cord circuit. In the figure, the line I represents any type of line, for example, a subscribers line, terminating at a switchboard in the jack 2. The signaling apparatus normally associated with such line has been purposely ornitted for the sake of simplicity since it forms no part of the invention. A cord circuit 3 having plugs 4 and 5 is intended to connect the line I with other lines such as 6 and. 8. That is accomplished by inserting the rear plug 4 in the jack 2 and a front plug 5 in the jacks 9, II] or I I, in which the lines 6 and 8 terminate at the switchboard. For the purpose of illustrating this invention a plug I2 of a cord circuit shown in fragmentary form, is .represented as being in engagement with the jack 9. That jack is also connected in parallel with the contacts of jack II]. The relay I3 associated with the circuit 3 is the busy-test relay and serves to keep the tip conductor of the cord circuit open until after the front plug has been inserted in the jack of the line over which it is intended to establish communication.

The key It is intended to connect the operator's telephone set across the conductors of the cord circuit. That is done by connecting the outer terminals of windings I5 and I6 of the induction coil 31 to the contacts of the switch I4 and by connecting the inner terminals of those windings together so that those windings of the induction coil will be connected across the cord circuit when the switch is operated. The winding I6 is connected by the conductors I1 and I8 to the sleeves of the jacks I9 and 20. Those jacks are intended to cooperate with the plugs 2| and 22 of the operators telephone set, which includes the receiver 23 and the transmitter 24. The tip contact of jack 20 is connected to a source of potential 25 and the tip contact of jack I9 is connected to the secondary winding 26 of the induction coil 31 so that when the plugs 2| and 22 are inserted in the jacks I9 and 20, respectively, current will flow from the source 25 through the transmitter 24, and thence through the winding 26 to ground. The jacks 21 and 28 are intended to cooperate with the plugs 29 and 30 of the supervisors telephone set, thereby facilitating the connection of that set to the operators telephone circuit.

The transmitter branch of the supervisors telephone set includes a switch 3i, the purpose of which willbe understood from the description of the mode of operating this circuit. The induction coil 32 comprises three windings one of which, 33, is connected to the upper contact of the busy-test relay l3 and serves, in cooperation with winding 36, to give the busy test to the operator by producing a clicking sound in her receiver. The winding 34 is bridged across the winding I6 of the other induction coil 31, across which are connected the conductors I1 and I8 of the receiver circuit of the operators telephone set. The third winding, 35, of the induction coil 32 has one of nected to the upper contact of the relay 36. The lower contact of that relay is connected to one of the terminals of winding 32. The winding of relay 36 is connected in series with the source of potential 25 and the transmitter of the supervisors telephone set when the plugs 29 and are inserted in the jacks 2'! and 28. That transmitter branch also includes the winding 26 of the induction coil 31.

The nature of the invention will be clear from the following description of the mode of operation of the circuit in the handling of a call. Let it be assumed that a subscriber connected to the line I is calling another party. The operator, upon the operation of the signal (not indicated), inserts the plug 4 in the jack 2 and at the same time throws the listening key M, thereby effectively connecting her telephone set to the said line. The operator's circuit at that instant may be traced from the upper contact of switch hi to the outer terminal of winding l 5, thence through the said winding and over conductor I! to the sleeve contacts of jack l9 and plug 25,. thence through the receiver 23 and through the sleeve contacts of plug 22 and jack 23, and thence over conductor I 8 to the other contact of switch l4. That connects the receiver to the cord circuit and at the same time the transmitter 24 is effectively connected thereto through the windings 26, I5 and I6 of the induction coil 31. The transmitter will be energized by the source of potential 25. The operator is then capable of talking to the subscriber connected to line i and also of receiving from the subscriber the number of the called party. The lines 6 and 8 in front of the operator may be either subscribers lines or trunks to a distant oflice.

Assuming that the called party is in another central ofiice district reached by the trunk circuits 3 and 8, the operator will then test those trunks in front of her to obtain an idle one. This she does by touching the tip of the plug to the sleeve of the jack in the usual manner. If the tip of the plug 5 touches the sleeve of the jack III, which is multipled in another position with jack 9, she will receive a busy test from the battery that is connected to the sleeve of the jack 9. That result-is effected by the flow of current from that battery over the sleeve contacts of jacks 9 and I0 and through the tip contact of plug 5, the upper contact of relay l3 and the winding 33 of the induction coil 32. The current that flows through that winding will induce an impulse in winding 34 which will be impressed across conductors i I and I8 and will produce a click or clicks in the receiver 23 of the operators telephone set. The operator will thereupon test another line, such as 8, in a similar manner, and upon getting no clicks will insert the plug 5 into the jack II. This will cause the operation of relay l3, which disconnects the busy-test winding 33 from the cord circuit and establishes a through connection between the tip contacts of the plugs 4 and 5.

Now, let us assume that the supervisor wishes to supervise such connection and perhaps to talk to the parties. This is accomplished by inserting the plugs 29 and 30 into the jacks 2? and 23. Thereupon the receiver of the supervisors telephone set will be connected to the winding of the induction coil 32, the connection including the upper contact of relay 36, the sleeve contacts of jack 28 and plug 33, the said receiver, the sleeve contacts of plug 29 and jack 21, and the said winding 35. Winding 35 is so proportioned with respect to Winding 34 that the impedance of an ordinary telephone receiver, such as 23, of the operators telephone set, will be stepped up by the windings 35-34 so that the supervisors receiver will have high impedance as compared to the receiver of the operators telephone set. Consequently, the establishment of such a monitoring connection by the supervisor introduces substantially no loss or impairment of reception in the operators telephone set which, of course, is connected at the same time. Furthermore, that desirable effect has been attained even though the receiver employed in the superviscrs telephone set is the same type as that employed in the operators telephone set. The desirable result has been attained by connecting the supervisors receiver in series with the third Winding of the induction coil 32, which gives the same efiect as if a high impedance receiver has been connected directly in parallel with the receiver 23 of the operators telephone set.

Now, let it be assumed that the supervisor desires to talk to the parties connected to the lines that are joined by the cord circuit 3. To do so the supervisor presses the key 3! which connects her transmitter to the circuit, the connection including the source of potential 25, the winding of relay 36, the tip contacts of jack 28 and plug 30, the said transmitter, the key 3|, the tip contacts of plug 29 and jack 21, and the grounded winding 26. Current will, of course, flow through the transmitter and the speech variations will be induced by the winding 26 in the windings l5 and I6 and will be impressed across the cord circuit and the connected lines. There is, however, another and important effect. When the key 3| was closed, relay 36 was energized and its armature moved downward, opening its upper contact and closing the lower. The effect of that is to cut out of the receiver circuit of the supervisors telephone set the winding 35 and to connect the receiver of that set directly across wi'nding 34, which is conductively connected across the .same terminals of winding l6 as the receiver 23 of the operator's telephone set. The supervisors receiver, therefore, has its normal impedance, which is the same as that of the operators receiver, and consequently the supervisor would receive, as well as the operator, and both could talk with equal facility to the parties connected to the lines.

It would, of course, be possible to employ a separate transformer to step up the impedance of the monitoring receiver instead of using an additional winding, such as 35, upon the busytest coil 32. The use of a combined busy-test and monitoring coil provides a substantial saving in apparatus, and is considered a valuable feature of this invention.

It is desirable to point out that if the operator were to plug into jacks 21 and 28 instead of jacks l9 and 20, which are the normal ones for her to use, there would be no operating diiiiculty and no impairment of transmission.

This will be apparent when it is realized that;

there is no key in the operators transmitter branch of her telephone set. Consequently, when the plugs 2| and 22 of her set are inserted in the jacks 21 and 28, relay 36 will be operated and her receiver will be effectively connected across the winding l6 as are also the conductors I1 and I8.

Although the invention has been described in connection with its use by a supervisory operator at a telephone switchboard, it is not so limited but is capable of being used for supervisory purposes at places upon the telephone system other than at the central oflice. As an illustrative case reference will be made to so-called secretarial service wherein a secretary of a subscriber may listen in upon the conversation between that sub scriber and a distant subscriber without introducing any substantial loss in reception, and may, by operating the key of her head-set be able to talk to the distant subscriber if such action is necessary.

While the invention has been described in a single form, it is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. An operators telephone circuit adapted to have connected thereto an operators telephone set and a supervisors telephone set, both sets being substantially identical in their electrical characteristics, the said telephone circuit including means for connecting said sets to said circuit, the circuit being so arranged that the connection thereto of one of said telephone sets will introduce substantially no receiving loss in the other telephone set connected to the said circuit.

2. An operators telephone circuit including an induction coil, an operators telephone set, a supervisors telephone set having a switch in the transmitter branch thereof, both sets being substantially identical electrically, a second induction coil having a plurality of windings, and means controlled by the switch of said supervisors set to connect the receiver thereof to one or the other of the windings of said second induction coil whereby the impedance of the receiver branch of the said supervisors telephone set is made substantially equal to or greater than the impedance of the receiver branch of the operators telephone set.

3. In an operators telephone circuit, the combination with a plurality of operators telephone sets each comprising a, transmitter and a receiver, of means to connect said sets to the remainder of said circuit, and means connected to said circuit and responsive to the operation of a switch associated with one of said sets to effectively change the impedance of the receiver than that of the operators receiver branch,

depending upon the position of said switching means.

5. An operators telephone circuit including an induction coil having one of its windings effectively bridged across a cord circuit, an operators telephone set having its receiver connected across a part of the said bridged winding and having its transmitter connected in series with a source of potential and the other winding of said induction coil, and a second induction coil having three windings one of which is effectively bridged across that portion of the said bridged winding of the first induction coil to which is connected the receiver of the operators telephone set, a second operators telephone set including a transmitter and a receiver, the transmitter being connected in series with said source of potential and said other winding of the said first induction coil, the connection including a transmitter cut-out switch and the winding of a relay, the said receiver of the second set having one of its terminals connected to the armature of the said relay and having its other terminal connected to a terminal of the said bridged winding of the said second induction coil and also to a terminal of a second winding of the same coil, the other terminal of each of the said mentioned windings of the said second coil being connected to the contacts of said relay in such manner that the said receiver will be connected to the said bridged winding of the second coil whenever the switch of the transmitter circuit of the said second operators set has been operated to permit the flow of current through the said transmitter.

EGINHARD DIETZE. 

